An actuator using a piezoelectric composition is an element taking advantage of a piezoelectric phenomenon that a mechanical strain and a stress are generated when an electric field is applied. Such an actuator is capable of providing a minute displacement in a highly precise manner and also possesses characteristics such as a high initiation stress. For example, such an actuator can be used for the positioning in a precision machine tool or an optical device. As the piezoelectric composition used in this actuator, the lead zirconate titanate (Pb(Zr, Ti)O3) can be listed here.
However, such a lead zirconate titanate based piezoelectric composition contains a lot of Pb, so a problem arises recently that the Pb dissolved in the acid rain will have a bad influence on global environment. Thus, it is desired to develop a non-lead based piezoelectric composition free of Pb instead of lead zirconate titanate based piezoelectric composition.
For instance, in Patent Documents 1 and 2, a non-lead based piezoelectric composition composed of lithium potassium sodium niobate has been disclosed to have a curie temperature as high as 350° C. or higher and also have an excellent electro-mechanical coupling factor kr.
Further, in Patent Documents 3 and 4, a lithium potassium sodium niobate based piezoelectric composition and a piezoelectric composition containing a tungsten bronze-type oxide and a perovskite-type oxide have been disclosed as the non-lead based piezoelectric composition exhibiting a relatively large displacement amount.